Ask James Cregg about Matt Kalil's skills, long-term potential and the defining moments that proved his worth during an All-America career at Southern California, and Cregg needs a second. After all, USC's offensive line coach has an extensive mental catalog to sift through.

His first instinct is to point to last season's game with Washington, a blowout victory throughout which Kalil seemed to be snarling like an angry Rottweiler.

The Trojans had lost 32-31 at home to the Huskies a year earlier. Something about that stumble really agitated Kalil.

Cregg sensed as much during the rematch last November yet took even greater notice when he watched the game again. As USC's offense piled up 426 yards, including 252 on the ground, during a 40-17 victory, Kalil repeatedly demolished Huskies defenders like a bulldozer uprooting a tulip garden.

"You put that game on and you instantly see a guy with a chip on his shoulder," Cregg said. "You see who Matt Kalil is, a fierce competitor who is doing everything he can to bury his man. That was Matt's passion at its best. That's his determination to win every block he has."

Statistically, Kalil succeeded in that mission in 2011, not allowing a sack in 457 passing attempts.

Yet if you want a more current gauge of his worth, Cregg offers that, too. As USC's spring practice unfolded in March and April, that once impenetrable safe door on the offensive line suddenly had a loose hinge.

"If I didn't fully appreciate what Matt meant to our offense, I understand it now," Cregg said. "Not having him here, I can tell you we miss him dearly already."

At this point, with the NFL draft four days away, it's difficult to find even a small collection of Kalil detractors. Ask the folks who have studied the star left tackle -- the NFL coaches, scouts, general managers and draft analysts -- and they all will sing a similar refrain: Kalil is as close to a can't-miss offensive line prospect as you'll find.

He's strong and athletic. His feet are quick, and his reach packs power. Best of all, he has an undeniable ferocity that fires his ambition to get better.

Realistically, Kalil could be a perennial Pro Bowler for the next 10 to 12 years.

Given all that, it seems insane to even entertain the thought that the Vikings, owners of the No. 3 pick and hoping to bolster their line, would consider passing on such an obvious standout.

So why might the decision prove more complicated?

Return on investment

Over the next four days, Vikings General Manager Rick Spielman will revisit every detail of his voluminous research on the left tackle position in an attempt to answer one question: Just how much can a standout lineman like Kalil catalyze the growth of a rebuilding team?

As crazy as it might sound, the Vikings cannot select Kalil solely because he projects as a future Hall of Famer who will provide a sturdy wall of protection for the next decade. That alone, unfortunately, does not guarantee significant team success.

Take Willie Roaf, who was elected into the Pro Football Hall of Fame in January. Roaf was drafted eighth overall by the Saints in 1993 and enjoyed a 13-year career that included 11 Pro Bowl appearances. Yet during his nine years playing tackle for New Orleans, Roaf was a part of exactly one playoff team.

And what about Joe Thomas, five times a Pro Bowler during his five seasons in Cleveland? Well, since drafting Thomas third in 2007, the Browns have gone 28-52 with no indications a resurgence is ahead.

So just how valuable has it really been for Cleveland to have a consistent star on the offensive line?

"You've got to really weigh your options," Frazier said. "Because the philosophy [in the NFL] has always been to get the game-changer. And left tackle is not necessarily the game-changer. Usually game-changers are the guys who can score you points. Receivers. Quarterbacks. So what are we measuring that left tackle against? It's a loaded debate."

Comfort zone

Between 2001 and 2010, 14 NFL teams invested a top-10 pick on an offensive tackle. From that fraternity, nine of those linemen never have been part of a playoff victory. And only Jordan Gross, Levi Brown and D'Brickashaw Ferguson have made it as far as the conference championship game.

Former Browns coach Romeo Crennel was part of the brain trust that locked in the Joe Thomas pick five years ago. Without question, Thomas has become exactly the player Crennel envisioned.

Sturdy. Consistent. Dominant.

Yet, to date, Thomas' brilliance has paid few dividends. Cleveland started seven different quarterbacks during Thomas' career and had three head coaches.

So what should the Vikings be considering as they measure Kalil's value? Crennel, now the head coach in Kansas City, believes the left tackle discussion has to center on the projected comfort that O-line prospect can provide his quarterback.

In other words, the Vikings must sidestep the idea that Kalil's arrival will instantly accelerate their rise back to relevance. But if the Vikings firmly believe Kalil's steadiness will help quarterback Christian Ponder ascend quickly, then the pick is a no-brainer.

"If you have a quarterback who has confidence in the guys protecting for him, when he has to throw, he is more at ease," Crennel said. "He can look down the field for the routes. He doesn't have to look at the protection or the rush. And I think that value, in itself, is hard to measure. If you get a left tackle who provides that for your quarterback, then I think your whole offense can be better in a hurry."

Kalil, with an obvious vested interest in the discussion, echoes Crennel's assessment.

"It's about making that quarterback feel more comfortable in the pocket, that he can trust that he can get that extra read and get that extra second knowing he's not going to be getting hit from behind or speared in the back," Kalil said. "I think a quarterback's confidence is everything."

'Take the tackle'

Now might be a good time to mention the Vikings allowed 49 sacks last season. Ponder was sacked 30 times in 10 starts and suffered a painful hip pointer in Week 13 that hindered him in losses to Denver, Detroit and Chicago. He also was knocked out of a Christmas Eve victory at Washington because of a concussion.

Frazier and Spielman still believe Ponder is their long-term answer yet concede he needs to show marked growth in Year 2. That's a goal that will be reached only if Ponder can retain his health and remain at ease in the pocket.

Which might bring this draft debate full circle.

Paging: Matt Kalil.

According to ESPN draft expert Todd McShay, Kalil is the surest bet for the Vikings at No. 3, a pick that needs to be made unless an incredibly lucrative trade offer surfaces.

Said McShay: "It would take a team blowing me away. Because you don't have many opportunities to get an elite left tackle and a guy that can protect your investment. Whether you believe Ponder's going to be a great quarterback or not at all, bottom line is you drafted him high last year. ... So you've got to do everything you can to put him in the best situation to succeed. I think right now, unless you get multiple picks who can come in and be successful and productive players around that quarterback, just go ahead and take the tackle."